Addressing Psychiatrist Workforce Shortages in the U.S. with Psychiatric Advanced Practice Registered Nurses (APRNs) Project Summary/Abstract The U.S. is experiencing a severe shortage of psychiatrists, which greatly limits access to behavioral health (BH) treatments for many individuals, including some of the most vulnerable with serious and persistent mental illnesses (SPMI). While psychiatric advanced practice registered nurses (APRNs) are uniquely qualified to alleviate BH prescriber shortages, there are several barriers that limit their ability to practice to the fullest extent of their licensure and training. Although APRNs have prescriptive authority in all U.S. states, whether their prescriptive management must be supervised by a physician varies by state. As of 2016, only 22 states and DC allow for fully independent prescriptive authority among APRNs while the remaining 28 states restrict their prescribing autonomy. These state-based regulations are frequently cited as barriers to full utilization of psychiatric APRNs. Past efforts to expand the scope of APRNs? prescriptive authority have met with significant opposition by physicians and prominent professional organizations who cite patient safety concerns. There are also concerns that expanding APRNs? prescriptive authority does not result in any overall net increase in the availability of medications, because APRN prescribing will merely replace or ?crowd out? physician prescribing. The proposed study will be the first to capitalize on an ongoing natural experiment to inform the policy debate surrounding the expansion of APRNs? prescriptive authority as one approach to addressing the significant psychiatrist-prescriber workforce shortage in the U.S. The proposed project will use the 50-state Medicaid Analytic eXtracts and related Medicare Part D data from 2010-2013 to evaluate prescribing of BH (i.e., antipsychotic, mood stabilizer, antidepressant, and alcohol use disorder) medications in Medicaid enrollees with SPMI (i.e., schizophrenia spectrum disorders, bipolar disorder, major depression, co-occurring alcohol use disorders) by psychiatric APRNs and psychiatrists. Propensity score matching will be the primary mechanism to control for selection bias, and generalized linear mixed models will be used to analyze the propensity score- matched datasets to address the following specific aims: (1) To compare prescription of guideline-concordant BH medications and treatment continuity (adherence, persistence) among patients with SPMI treated by psychiatric APRNs versus psychiatrists; (2) To determine the effects of states permitting APRNs to prescribe autonomously on prescription of guideline-concordant BH medications and treatment continuity (adherence, persistence) among patients with SPMI. As an additional aim, we will leverage recent changes in state prescriptive authority regulations in Maryland to evaluate whether allowing psychiatric APRNs to prescribe autonomously has led to a net increase in prescriptions for BH medications for SPMI compared to other states where APRNs have independent practice but not prescriptive authority: (3) To investigate the effects of states permitting APRNs to prescribe autonomously on the overall availability of BH medications to patients with SMI and on crowding-out psychiatrist prescribing.